The purpose of this application is to support an ongoing program of research aimed at determining risk and resilience factors in the evolution of psychopathology in an internationally unique cohort of young people with mental retardation that forms the Australian Child to Adult Development (ACAD) Study. The broad aims of this application are to 1) study the course and pattern of psychopathology in children with mental retardation; 2) examine potential biopsychosocial risk and protective factors which may be associated with psychopathology; and 3) evaluate and refine the measurement properties of the DEC, the principal instrument used to assess psychopathology in this study and in broad use internationally. [unreadable] [unreadable] The fourth wave of the ACAD study (14 years of follow-up) has now been completed and permits analysis of the development of psychopathology from childhood through adolescence to young adulthood. Advanced statistical methods, including growth mixture models, will be used to identify developmental trajectories of emotional and behavioral disturbance in these groups, to investigate risk, mediating and moderating factors, and to empirically delineate subpopulations showing distinct patterns of change over time. A separate aim is to evaluate and refine the psychometric properties of the Developmental Behavioral Checklist (DEC) in the longitudinal ACAD study and in several international cross-sectional datasets. The analysis of psychometric properties of the DEC will use new developments for multiple-group factor analysis of categorical data and item-response models to construct and evaluate a short-form measure of psychopathology. [unreadable] [unreadable] This application provides an extraordinary opportunity to evaluate the mental health pathway of this vulnerable population through the transition into adulthood. The unifying purpose of this project is to apply advanced statistical modeling techniques to the existing ACAD data and to strengthen the findings by incorporating comparable data collected in a number of other countries. [unreadable] [unreadable]